Cherry eye

Cherry eye is a disorder of the nictitating membrane (NM), also called the third eyelid, present in the eyes of dogs and cats.[1] Cherry eye is most often seen in young dogs under the age of two.[2] Common misnomers include adenitis, hyperplasia, adenoma of the gland of the third eyelid; however, cherry eye is not caused by hyperplasia, neoplasia, or primary inflammation.[3] In many species, the third eyelid plays an essential role in vision by supplying oxygen and nutrients to the eye via tear production.[4] Normally, the gland can evert without detachment.[3] Cherry eye results from a defect in the retinaculum which is responsible for anchoring the gland to the periorbita. This defect causes the gland to prolapse and protrude from the eye as a red fleshy mass.[3] Problems arise as sensitive tissue dries out and is subjected to external trauma[3] Exposure of the tissue often results in secondary inflammation, swelling, or infection.[3] If left untreated, this condition can lead to Keratoconjunctivitis sicca (KCS) and other complications.[4]

Cherry eye is not considered a genetic problem, as no proof of inheritance have been determined.[6] The NM contains many glands which merge and appear as a single gland.[7] Typically, glands secrete tears for lubrication of the cornea.[7] Lack of anchoring allows gland to flip up, causing the gland to prolapse. Symptoms include a visible fleshy mass, abnormal tear production, and a discharge or drainage from the eye. Cherry eye is typically diagnosed by examination of the conjunctiva and nictitating membrane.[2] The most obvious symptom of cherry eye is a round fleshy mass through medial canthus of the eye, similar in appearance to the fruit it is named for.[7] This mass may be unilateral or ‘’bilateral’’. Both eyes may develop cherry eye at different times in the animal’s life.[1] Other symptoms of cherry eye include drainage from the eye and abnormal tear production. Initially, cherry eye results in overproduction of tears, but eventually changes to unsubstantial tear production.[1]

Cherry eye, if caught early, can be resolved with a downward diagonal-toward-snout closed-eye massage of the affected eye or occasionally self-corrects alone or with antibiotics and steroids.[3] Sometimes the prolapse will correct itself with no interference, or with slight physical manual massage manipulation as often as necessary coupled with medication.[3]

Surgery is the most common means of repairing a cherry eye. Surgery involves gland replacement, not excision, by anchoring the membrane to the orbital rim.[3] In severely infected cases, preoperative antibiotics may be necessary by means of antibiotic eye ointment.[3] Removal of the gland was once an acceptable treatment, and made the eye appear completely normal.[5] Despite cosmetic appeal, removal of the gland reduces tear production by 30 per cent. Tear production is essential in maintaining and protecting the eye from the external environment.[5] Reduced tear production is especially problematic in breeds of animals predisposed to Keratoconjunctivitis sicca (KCS). With surgeries performed in this manner, KCS often results later in life.[3]

Close-up of prolapsed gland in small breed dog

KCS is common in dogs, affecting one per cent of the dog population.[8] KCS is a chronic degenerative conjunctivitis that can lead to impaired vision and blindness.[2] KCS has a wide array of causes including drug toxicity, cherry eye, previous surgery, trauma, and irradiation.[2] KCS can be treated, but treatment often spans the entirety of the animal’s life.[2]

In contrast to this, several replacement surgical procedures exist to remedy cherry eye.[2] Replacement of the gland results in lower instances of dry eye later in life.[9] Surgery types are broken into two groups: anchoring procedures and pocket/envelope procedures.[1] At least 8 surgical techniques currently exist.[1] In anchoring procedures, the prolapsed gland must be sutured to the periorbital fascia, the sclera, or the base of the third eyelid.[5] In contrast, pocket procedures involve suturing healthy tissue around the prolapsed to enclose and secure it.[5] Each of these techniques may be performed with an anterior or superior approach, depending on which direction of suturing will cause the least complications to the eye.[5]

Originally, the anchoring method involved suturing the gland to the globe. This method was superseded over time due to the risky and difficult nature of the surgery, along with a high rate of recurrence.[3] Anchoring approaches from posterior may disrupt normal fluid excretion.[9] Subsequently, an anterior approach was introduced.[9] Disadvantages of anchoring techniques include restricted mobility of third eyelid, which is essential in the functions of fluid distribution and self-cleaning.[9] New procedures are currently being explored to allow tacking of the NM without restricting movement of the third eyelid.[9] Few studies compare results of surgeries, therefore choosing a procedure is a matter of preference.[9]

The envelope method, often called the pocket technique, requires suturing of tissue around the prolapse, encasing it in a layer of conjunctiva.[5] Pocket techniques are easiest for doctors to learn.[1] Pocket methods also have anterior and posterior versions. Posterior suturing techniques are the most commonly used because they cause the least complications, with no alterations in tear production.[9] Surgery should only be attempted by experienced surgeons.[3] Inappropriate surgical techniques can result in many complications including cysts on the eye.[9]

Previously, treatment was thought optional until the role of NM was fully understood.[1] The NM gland is responsible for 40–50% of tear production.[10] If exposed for extended periods of time, the gland is at risk for trauma, secondary infection, and reduced tear production.[10] Many complications can arise if left untreated, early closed-eye massage manipulation is recommended to prevent inflammation .[3]

Postoperative treatment includes antibiotic eye ointment three times daily for two weeks.[5] With newer procedures, the rate of prolapse recurrence is minimal.[3] Most techniques have a reprolapse rate of approximately zero to four per cent.[1] Occasionally, additional or duplicate surgery is required.[10] With treatment, it is possible for animals to live a normal life.

^Christmas, R. E. (1992).But Some breeds are considered to be more susceptible to its development than others, including the Bulldog, Boston Terrier, Bull Terrier, Lhasa Apso, Cocker Spaniel, St. Bernard, Shar-pei, Shih Tzu and Poodle "Common Ocular Problems of Shih Tzu Dogs". Canadian Veterinary Journal, Volume 33, 392.